1. Field of the Invention
The present invention is directed in general to the field of pressure sensor devices. In one aspect, the present invention relates to a micro-electro mechanical system (MEMS) pressure sensor having an improved packaging scheme for producing low cost differential pressure systems.
2. Description of the Related Art
Micro-Electro-Mechanical Systems (MEMS) technology is increasingly used to integrate mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. For example, MEMS pressure sensors can be used in a wide range of applications, including industrial applications such as air conditioning, liquid level sensing and flow control. Depending on the nature of the application, two types of pressure sensors are commonly used: absolute pressure sensors and differential pressure sensors. An absolute pressure sensor is a sensor that has an electrical output related to the absolute pressure of an external environment with respect to a known, constant pressure. A differential pressure sensor, on the other hand, is a sensor whose electrical output is related to a difference in pressures between two regions, and typically includes a semiconductor membrane separating two ports coupled to two different pressure levels. While differential pressure sensors may advantageously be used with differential circuits to provide higher linearity and greater noise immunity than the single-ended circuits typically used with absolute pressure sensors, there are significant technical challenges to using differential pressure sensors since one or both sides of the differential pressure sensor might be in close proximity to water or other corrosive chemicals. To protect against the corrosive environment, pressure sensors are provided with various coatings, encapsulants, or diaphragms made from various elastic gels, polymers, or other materials, but these protection schemes add to the complexity of manufacturing such sensors, resulting in increased cost, reduced reliability, and/or reduced ability to measure the pressure (e.g., due to the presence of a thick coating on the sensing diaphragm).
Accordingly, a need exists for an improved differential pressure sensor device and manufacture method which overcomes the problems in the art that have been discovered by the above-named inventors where various limitations and disadvantages of conventional solutions and technologies will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow, though it should be understood that this description of the related art section is not intended to serve as an admission that the described subject matter is prior art.